Are these things any good and worth the price? I know JET is reputable i just dont want to by a epoxy block with two resisters in it. I have a 95' XJ with nothing really perofrmance done yet... I am going to be getting a Borla Full Exhaust Header, Cat, and Cat Back Later in the summer. and A K& N intake along with making my TB larger.

Will the JET chip help lean out the already rich 4.0L and get me a little beter fuel economy?